Re: [IPsec] IV in ESP packets for AES-CBC and AES-CTR methods

[Stephen Kent <kent at bbn.com>]

At 7:40 PM +0530 5/11/09, ss murthy nittala wrote:
> Hi,
> Is it required for IV to be randomly generated for each ESP packet 
> in case of AES-CTR and AES-CBC methods?
>
> AES-CTR:My understanding is that IV is to be generated randomly for 
> the first packet.For each new outgoing packet increment IV and use 
> it.

Even for CTR mode, an explicit IV MUST be included with each packet, 
because the receiver does not know what method of counter value 
generation the sender has elected to employ.

Steve